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Start Point & End Point

Route Segment ICAO defines a route segment as

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For defining that the point used for the route segment is an RNAV waypoint (see also topic Designated Point (Overview)) the EnrouteSegmentPoint.waypoint attribute will be encoded with 'YES'.

In addtion AIXM 5 provides as an option to encode the extend of the route segment as geometrical element, using the Curve class. This data may be used for charting purposes. The curve will be encoded according to the corresponding GML specification (see topic Geometry (Overview)). It will contain the coordinates of the start and end point of the route segment. It has to be ensured that the data (i.e. coordinates) provided in the Curve element(s) match with those provided as start and end of the RouteSegment.

Implicit direction

As every route segment is defined 'from' a start point 'to' an end point, it has an implicit direction. This direction should be consistent with the direction of the route. The start point of a route should also be the 'from' point of the first route segment and the end point of the route should be the 'to' point of the last segment.

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Rules are included in the model to enforce consistency between the general direction of the route and the implicit direction of every segment (see below).

Track & Lenght

The RouteSegment class provides several attributes to define the initial trueTrack, initial magneticTrack, the initial reverseTrueTrack and the initial reverseMagneticTrack of it.

For "ENR 3.3 Area navigation routes", PANS-AIM explicitly requires that the magnetic bearing of the route segment is provided. For all other routes defined in ENR 3, PANS-AIM requires a track or VOR radial applying the following note

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According to PANS-AIM an the length of a route segment shall be provided as geodesic distance.

Lateral Limits

For "ENR 3.1 Lower ATS routes" and "ENR 3.2 Upper ATS routes", PANS-AIM requires the provison of lateral limits.

The RouteSegment class provides the attributes widthLeft and widthRight to define the lateral limits. These are the distances from the centreline of the route segment to the left and right edge respectivley. For example, if the route segment has a defined width of 10 NM for each of the attributes will carry the value '5' uom equal-to 'NM'.

Vertical Limits

PANS-AIM requires that all routes/route segments have at least a Lower lower limit and an Upper upper limit.

For some types of routes, viz. ENR 3.1 (Lower ATS Routes) and ENR 3.4 (Helicopter Routes), also minimum obstacle clearance altitudes and minimum flight altitudes, respectively shall be provided.

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The following table gives an overview which vertical limits are required by PANS-AIM for the AIP data set and the corresponding AIXM attributes of the RouteSegment class (Note 1) :

PANS-AIM

AIXM 5.1.1

Property

Definition/Desription

Relevance

Attribute

Description

Remarks

Upper limit

The upper limit of the route segment

ENR 3.1-3.4

upperLimit

The vertical position of the route segment ceiling.

Lower Limit

The lower limit of the route segment

ENR 3.1-3.4 (Note 2)

lowerLimit

The vertical position of the route segment floor.

Note

title	Note 2

According to PANS-AIM for ENR 3.1 Lower ATS Route,

lower limits or minimum en-route altitudes

shall be defined.

In the "old" ICAO Annex 15 it was

lower limits or minimum flight altitudes

Minimum obstacle clearance altitude (MOCA)

The minimum altitude for a defined segment of flight that provides the required obstacle clearance. minimumObstacleClearingAltitude

ENR 3.1 Lower ATS Route

minimumObstacleClearanceAltitude

Minimum obstacle clearance altitude (MOCA). The minimum altitude for a defined segment of flight that provides the required obstacle clearance.

According to PANS-OPS

A MOCA is determined and published for each segment of the route.

In PANS-AIM it is only required for ENR 3.1Lower ATS Routes.

The MOC value to be applied in the primary area for the en-route phase of an IFR flight is 300 m (1 000 ft) as a minimum.

Minimum en-route altitude (MEA)

The altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance.

ENR 3.1 Lower ATS Route (Note 2)

minimumEnrouteAltitude

Minimum en-route altitude (MEA). The altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance.

According to PANS-OPS

The MEA is the greatest of:
the MOCA;
the minimum altitude for proper reception of the relevant facilities;
the minimum altitude for proper reception of ATS communications;
the minimum altitude that complies with the ATS structure.

Minimum flight altitude

ENR 3.4 Helicopter routes

???

According to PANS-AIM

The criteria used to determine minimum flight altitudes shall be provided in GEN 3.3.5.

In PANS-AIM the term is only used for "ENR 3.4 Helicopter routes"

ICAO ANnex 11, 2.22 Minimum flight altitudes

Minimum flight altitudes shall be determined and promulgated by each Contracting State for each ATS route and control area over its territory. The minimum flight altitudes determined shall provide a minimum clearance above the controlling obstacle located within the areas concerned.

Info

title	Open question

Isn't acc. to Annex 11 the MOCA and the Minimum flight altitude for Routes ?

Or is both the MEA and the MOCA considered as a kind of minimum flight altitude (see also change for ENR 3.1. Lower ATS routes?

NA

minimumCrossingAtEnd

The lowermost vertical position at the end point, when flying on the route portion in the direction indicated in the RoutePortionUsage.

Warning

title	AIXM 5.1.1 issue

RoutePortionUsage is not defined in AIXM 5.1.1. If this attribute is related to the route portion, whay is it part of the RouteSegment class?

NA

maximumCrossingAtEnd

The uppermost vertical position at the end point, when flying on the route portion in the direction indicated in the RoutePortionUsage.

Same issue as above.

Note

title	Note 1

PANS-AIM defines more vertical limits, i.e Area Minimum Altitude (AMA) and Minimum Vectoring Altitude (MVA) which are not considered as part of the AIP Data set and hence are not conatined in the table.

Info

title	Open Question

In some State AIPs, an additional limit, "overriding" the Lower limit specification is published. To publish this minimum limit, often statements such as " but at least" are used. The Lower limit override always refers to ground e.g. "feet above ground".

How to encode this in AIXM 5.1.1? in AIXM 4.5 a dedicated attribute was provided VAL_DIST_VER_LOWER_OVRDE

Example:

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